Exemplary embodiments pertain to the art of power generation and, in particular, regulating a direct current (DC) voltage generated by a six-phase permanent magnet generator.
A conventional DC power generating system utilizes a 3-phase variable-speed permanent magnet generator (PMG) and an active rectifier. PMG's offers high efficiency and high power density in comparison with a wound-field synchronous generator. However, the size of the conventional two-level six switch active rectifier requires large size passive components, such as dc link capacitor and output power quality filter. Torque pulsation is sensitive to phase current harmonics. Torque ripple producing currents of 3-phase PMG is given by 6n±1 (n=1, 2, 3 . . . ).
A 6-phase PMG eliminates sixth harmonic torque pulsation caused by harmonic components in the stator current. To achieve high power density, multilevel topologies, such as an unidirectional Vienna Rectifier or a bi-directional neutral diode clamped multilevel converter, have been considered to achieve low harmonic distortion with moderate switching frequency and reduced EMI emissions compared to a standard 2-level active rectifier/inverter. However, these topologies are complex and expensive.